The present invention relates to a bag-boxing apparatus. More particularly this invention concerns a machine that takes a stack of flexible bags or the like from a stacking station, folds the stack, and places the stack in a box for shipment or further handling.
Bags, typically of plastic, are produced one after the other from a plastic tube and are formed into stacks at the end of the bag-production line. These stacks must be placed into some sort of container, normally a shipping carton, to which end the stack must be folded in half for most efficient packaging, as otherwise the package would be too large.
U.S. Pat. No. 3,640,050 of Nystrand discloses such a device where the stack of bags is first set atop a downwardly V-shaped folding plate so that the stack forms a downwardly open U-shape. This U-shaped stack is then gripped, flipped on its side, and pushed between a pair of folding blocks to produce a double fold in the stack. The patent is silent as to how the stack is held during the various picking-up, reorienting, and folding operations.
In U.S. Pat. No. 4,588,070 of Smith a bag-transfer device is described having a pair of grippers that can be set at different spacings to hold bags of different sizes. There is no discussion of how to use such a two-part gripper in a bag-boxing apparatus.
U.S. Pat. No. 4,056,202 of Steigler handles a stack of bags pinned together by a large holding staple that forms wicketing pins during the stacking operation and that subsequently is what is grabbed to move the stack of bags. This disclosure is also silent about any folding and boxing operation.
The transfer apparatus disclosed in U.S. Pat. No. 5,185,987 of Turvey has a system for folding a stack of flexible sheets and tucking the stack, fold-side first, into the jaws of a carousel-like transport device which then sweeps them over a slide so as to form a second fold, whereupon the twice-folded stack is stuffed into a container. This arrangement is fairly complex and is not readily adaptable to sheets of different sizes.
It is therefore an object of the present invention to provide an improved bag-packing system.
Another object is the provision of an improved bag-packing method which overcomes the above-given disadvantages, that is which surely and accurately picks up a stack of bags, folds it in half, and puts the folded stack into a container.
A further object is to provide an improved apparatus for carrying out the method.
A stack of flexible bags oriented horizontally in a stack station is packaged by first sliding a robot hand horizontally into position around an end portion of the stack with front and rear grabs of the hand aligned with edges of the end portion and another portion of the stack wholly outside the hand. Then the grabs are closed on the edges of the end portion with the front grab positioned inward of the stack from the back grab and the hand is raised and pivoted about a horizontal axis to fold the gripped stack about a fold line adjacent the front grab and to one side of which lies the gripped portion and to the other side of which lies the other portion so that the bag is given a downwardly open U-shape. The back grab is then released and reengaged around the folded stack to press the other portion against the end portion still gripped by the front grab. Then the hand is pivoted into a position with the folded and gripped stack oriented horizontally and the folded and gripped stack is positioned in an upwardly open container. The grabs are released and the hand is lifted out of the container to leave the folded stack therein.
Thus the system of this invention works extremely smoothly and can easily be used for bags of different lengths. It folds the bag stack with a simple movement and then deposits the folded stack into the container.
According to one procedure of this invention after forming the fold, the folded stack is set atop a fold plate and the front grab is released from the folded stack. Then the hand is raised, oriented with one of the grabs above the other, and then lowered it down over the folded stack on the fold plate. The hand thus makes three simple movements, a first one picking up the stack, forming the fold, and setting it on the fold plate, a second moving clear of the folded stack on the plate, and a third picking it up off the plate and setting it in the container. Such operation is very easy to program into standard industrial robot.
According to another feature of the invention after forming the fold the hand is pivoted sufficiently that the other portion comes to lie against the one portion held by the grab. Then the front grab is retracted from between the portions of the folded stack and reorienting outside the portions. Thereafter the front grab, as before, is brought back to clamp the folded stack in place. This system dispenses with the folding plate and allows the operation to be reduced to two sweeping movements of the hand, one picking up the stack and pivoting it back until it folds and the fold is captured and another pivoting back down and depositing the stack in the container.
In fact the stack can be formed into a multiple or Z-fold by closing the front grab on both portions of the folded bag while leaving an outer portion of the stack hanging from the front grab, pivoting the hand backward until the outer portion comes to lie against the outer portion of the folded stack, retracting the rear grab from between the end and other portions and engaging it back against the outer portion to press same against the end and other portions. This can be repeated as much as necessary to form a stack with as many folds as desired.
The folded stack is pushed down out of the hand into the container by a knockout device that can be carried on the hand. Furthermore it is possible to wrap a band around the folded stack.
The apparatus for packaging a stack of flexible bags oriented horizontally in a stack station has according to the invention a robot hand having front and rear grabs engageable with edges of an end portion of the stack with another portion of the stack wholly outside the hand, and control means for carrying out the above-detailed steps. The grabs are each formed by two pairs of jaws. The jaws of the front grab is operable independently of the jaws of the back grab. For the multiple-folding system means is provided for displacing one of the pairs of jaws of each grab away from the other of the pairs of jaws of the respective grab.